Electric furnace



YParental oct. 13, 1925.

UNITED STATES PATENT OFFICE.

ALVIN D. KEENE, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WESTINGHYOUSE ELECTRIC & MANUFACTUBIN G COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC FURNACE.

Application illed August 18., 1923. Serial No. 658,031.

To all whom t may concern:

Be it known that I, ALVIN D. KEENE, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric Furnaces, of which the following is a speciflcation.

My invention relates to electric furnaces and particularly to electric arc furnaces.

One object of my invention `is to provide an electric furnace having'a relatively small high-temperature heating element.

Another object of my invention is to provide an electric furnace having an arc heating element that shall operate with only an occasional adjustment thereof.

Another object of my invention is to provide an electric furnace having a heating element that shall comprise an arc that is entirely surrounded by one of the electrodes to increase the heat distributing area thereof.

Another object of my invention is to provide an elect-ric furnace that shall comprise an arc and means forradiating heat generated thereby at a temperature substantially lower than that of the arc.

Another object of my invention is -to provide a heating element that shall permit of easily and quickly varying the amount of heat generated thereby.

In practicing my invention, I provide a formed block of carbonaceous material having an opening'therein. An elongated carbonaceous electrode of smaller dimensions in cross-section than the o ning has one of its ends extending into saidbpening, and means are provided for adjusting the position of the electrode longitudinally.

Av plurality of refractory electric-conducting members are located in face-to-face relation relatively to each other, one of the end members operatively engaging the block and the other end member operatively engaging a terminal member.

In a modification of my invention, I provide a single carbonaceous block having a plurality of o enings therein angularly disosed relative y to each other, each opening raving an elongated electrode extending therein.

In the single sheet of drawings,

Figure 1- is a view, in vertical sect-ion, of an electric furnace embodying my invention,

Fig. 2 is a view, in vertical section, of an electric furnace comprising a modified form of my invention, and

Fig. 3 is a top plan view of a heating element illustrated in Fig. 2 and a portion of the adjacent furnace structure.

An electric furnace 11 comprises a plurality of refractory walls 12 constituting the side, bottom and top portions .thereof and comp-rising a plurality of bricksor blocks of a heat-insulating material. An inner lining 13 may comprise a suitable high-temperature resisting refractory material. hinged cover`member 10 is provided, although its use is not required and such use depends entirely upon the type of construction of the furnace body.

A heating element forthe furnace 11 comprises a relatively small block 14 of carbonaceous material that may be substantially circular in section and have an opening 15 extending into one end thereof. An elongated carbonaceous electrode 16 extends through a suitable opening 17 in the top of the furnace structure and has its lower end located in the opening or chamber 15 of the block 14.

Means for` adjusting the position of the elongated electrode 18 may comp-rise any suitable or desired means, here illustrated as a clamping and terminal member 18. one end of which holds the electrode 16 and the other end of which is adjustably supported in a screw-threaded rod 19, the lower end of which is rotatably supported in a suitable member 21 mounted on the furnace structure.

A hand wheel 22 is secured to the upper end of the shaft 19 for causing a turning movement of the shaft 19 whereby the position of the electrode 16 may be adjusted longitudinally and relatively to the block 14. While I have illustrated a specific embodiment of adjusting means, I do'not desire to be limited' thereto, as any suitable means, either manually or automatically controlled, may be employed.

A supporting block 23 of suitable refractory carbonaceous material is provided, to which a terminal member 24 is suitably secured and extend outwardly through the furnace structure. One end of a suitable supply circuit conductor is connected to the terminal member 24 and the other supply circuit conductor is connected to the mem- /ber 18. The block 14 may rest directly upon the block 23 or a plurality of refractory electric-conducting members 25 may be located between the blocks 14 and 23 whereby a resistance is interposed between the block 14 and the supporting member 23.

In operation. the terminal members 18 and 24 are connected to a suitable source of electrical energy and the electrode 16 is caused to operatively engage the block 14 at the bottom of the o ning 15, but is then caused to move away t erefrom, whereby an arc is produced between the lower end of the electrode 16 and the 'side and bottom walls of the opening 15 in the block 14.

I have found by actual experiment that an arc of this kind o crates satisfactorily for relatively lon perlods of time without any attention w atsoever. I have also found it possible. to have an ordinary workman ilse a` furnace of this type for heattreating metal objects or for heating metal rods without more attention than he could give it without interfering with his work, and it is in fact necessary to readjust the electrode only a few times during a workin day.

ere the temperature is an important element, as in heat treating, any commercial type of pyrometer may be employed in the furnace chamber to indicate the temperature and an ammeter may be employed to determine the current traversing the arc in order to permit of closer observation of the amount of energy being translated into heat.

The load can be varied over a relatively wide range by adjusting the position of the electrode relatively to the block. The temperature of the electric arc generated in the block. 14 is, of course, relatively high, but this arc is entirely surrounded by a refractory material that Withstands the relatively high temperature of the arc and whose surface acts as a radiating surface for the heat produced by the arc. The temperatuie of the surface of the block 14 is very much lower than that of the arc and if the block 14 is of suitable size and contour, the heat distribution therefrom will be uniform.

As there is no mutil between the heatradiating surface which, as statedabove, isl

the surface of the block 14, and the material being heated, the furnace temperature responds very quickly to changes in the energy being translated into heat and -it is to be noted further that heating is by direct radiation from the surface of one of the electrodes, more particularly the block 14.

As the arc is substantially an embedded one, the oxidizing action of the surrounding atmosphere upon the two electrodes is and this may relatively small, thereby resulting in a relatively low consumption' thereof. As the temperature of the surface of the electrodes is relatively low, `the brick work of the furnace structure `is not subjected to unduly high temperatures as is the case where an open arc is employed and where relatively large amounts of energy are thereby translated intq heat. This also means that the dimensions of the furnace structure may be kept down to relatively small values, providing, of course that the character of the work to be placedl therein will permit.

The use of the auxiliary resistor plates 25 permits of providing a steadying resistor be of value in some cases, although I have found it possible to use the arc without any steadying resistor and still obtain satisfactory operation of such a furnace.

However, the use of carbonaceous members, as resistors connected in series circuit relation to the hereinbefore described electric arc, permits of obtaining greater variations in the amount of energy being translated into heat. For instance, I may cause the furnace to be heated up very quickly by so adjusting the length of the arc that a relatively large amount of energy is translated into heat in the arc itself. If, for instance, I employ a sufficient number of resistor members 25, it may be possible to extinguish the arc entirely for short lengths of time by causing the electrode 16 to operatively engage the block 14, whereby a banking action o'f the source of heat may be obtained over short periods of time.

I have illustrated a metal melting furnace in Fig. 1, of the drawing, a suitable hearth or bath 26, of substantially circular or annular contour, being provided in the bottom vof the inner lining 13. A door 27 and a pouring spout 28, having a closure block 29 associated therewith, are illustrated in Fig. 1 of the drawing.

I have illustrated a heat treating or metal heating surface in Fig. 2 of the drawing, which also illustrates a modification of my invention. An elongated block 31, of substantially cylindrical form, is supported in a furnace structure 11 of substantially the same general construction as hereinbefort` described, by suitable refractory electriciasulating side members 32 operatively engaging the ends only of the block 31.

The block 31 is provided with a plurality of openin 15 extending laterally into the block andsocated in spaced relation therein and anlarly disposed relatively to each other. lectrodes 16 extend into the furnace structureand into the o enin'gs 15 and may be adjustably su ported) by either the means illustrated in ig. 1 or by any other suitable or desired means usually employed in the art for such purposes.

The su ply circuit conductors, not shown, are suita ly connected to the outer ends of the electrode 16y whereb two arcs are produced within the bloc 31, connected in series circuit relation. Metal objects to be heat treated may be placedv in the furnace chamber 33 provided within the furnace structure 11, suitable doors (not shown) bcing provided to permit of inserting the metal objects into and removing them from the furnace chamber 33. The objects to be heated or heat-treated may be placed either underneath the block 31 intermediate of the two supporting members 32 or the side thereof, as may be suitable or as the' method of heating or of heat treating may require.

The structure embodying my invention thus provides an electric furnace having a heating element of relatively small dimensions wherein the heat is produced at relatively high temperature by an arc which is substantially entirely surrounded by refrac- `tory electric-conducting material that serves to radiate the heat produced by the arc at a lower temperature. The construction embodied in this device permits of operating an arc over relatively long periods of time, say several hours, without any adjustment of the vrelative positions of the two electrodes without serious change in the amount of electric ener being translated into heat. This latter con ition permits the use of such furnace by an ordinary Workman Without it interfering seriously with the work he is called upon to do in the handling of the metal objectsl to be heated or heat treated in the furnace chamber.

Various modifications and changes may be made herein without departing from the s irit and scope thereof, as set forth and c aimed in'the appended claims.

I claim as my invention:

1. In an electrically heated device, in combination, a formed block of carbonaceous material having an opening therein, a plurality of flat carbonaceous members located in abutting relation relatively to each other, one end of said set of members being in operative engagement with and supporting said block of carbonaceous material and the other end of said set of carbonaceous members being in operative engagement with a supply circuit terminal, and an elongated earbonaceous electrode, one end of which projects into the opening in said block and the other end of which is connected to a supply circuit terminal.

2. In an electrically heated device, in combination, a heating element comprising a formed block of carbonaceousmaterial having an opening therein, an electrodeco-operating With said block to produce an arc locate in the opening in said block and a resistor member comprising a plurality of refractory electric-conducting members operatively engaging said block and connected in series circuit relation to said are.

3. In an electric furnace, in combination, a formed `block of carbonaceous material having an opening therein, a carbonaceous electrode extending into said opening, a pluralit of carbonaceous resistor members locate in face to face relation and one of the end members operatively engaging said block and supporting the same, and means for permitting an electric current to traverse said members, said block and electrode in series circuit relation.

In testimony whereof, I have hereunto subscribed my name this- 13th day of August 1923.

ALVIN D. KEENE. 

